Various methods of providing multimedia conferencing services with guaranteed performance have been developed. Multimedia conference calls require a large amount of communication bandwidth. The subscribe loop plants of most telephone companies consist primarily of unshielded twisted pair copper (UTP) access lines of approximately 24 to 26 gauge size wire. The unshielded twisted pair copper wire has an asymmetrical nature of bandwidth, due to signal attenuation, that is proportional to length and frequency, and is known as an asymmetric digital subscriber line (ADSL). A modem that uses asynchronous transfer mode (ATM) protocol and an asymmetric digital subscriber line (ADSL) to transmit and receive signals is known as an ATM ADSL modem. Currently, some ADSL modems realize downstream rates of approximately 9 megabits per second (Mbps) and upstream rates of 1.5 megabits per second (Mbps). The ADSL Forum and T1E1.4 standard organizations are now developing standards directed to the manner in which ADSL modems will carry high-speed digital signals over unshielded twisted pair ADSL lines. Recent improvements in ADSL technology have created an opportunity to provide two-way multimedia conferencing, in addition to voice communication, over an unshielded twisted pair ADSL line. Unlike "tree-type" cable television (CATV) hybrid fiber coaxial (HFC) plant topologies, an unshielded twisted pair ADSL line provides point to point dedicated bandwidth. Therefore, ADSL lines do not require a sophisticated mechanism to share the bandwidth among multiple users (as is required for IEEE 802.14 hybrid fiber coaxial (HFC) medium access control (MAC) protocol).
However, although the asymmetrical nature of the upstream and downstream bandwidth distribution of an ADSL loop plant makes it attractive for one-way communication, such as video-on-demand (VOD), it requires different intelligent networking technologies for two-way communications (especially for multimedia conferencing over an unshielded twisted pair (UTP) asymmetric digital subscriber line (ADSL) access network).